(I) Field of the Invention
This invention relates to a gas distribution system which employs either header boxes or manifold systems having holes.
(II) Prior Art
In CO boilers (carbon monixide boilers) employing fluidized limestone to capture sulfur oxides, there is a need to remove spent limestone which has become sulfated. Since the sulfated limestone, when it leaves a CO boiler, often reaches temperatures as high as 1500.degree. F., it is necessary to cool such fluidized limestone to temperatures on the order of 350.degree. F. so that the cooled solids may be transported and handled by conventional conveyor systems, such as sold by Dynamic Air, St. Paul, Minn. An example of a limestone fluid bed boiler known in the art would be one sold by Foster-Wheeler Corporation, Livingston, N.J. An example of a waste bed cooler to reduce the temperature of spent limestone (calcium oxide, managenese oxide, and other materials that are employed in such CO boilers) is one sold by Procedyne Corp., Box 1286, New Brunswick, N.J. The CO boiler, the conveyor and the waste bed cooler per se are not a part of this invention.
One problem of commercially available waste bed coolers for solids is that the air distribution system employed to maintain a fluidized bed of solid particles therein over a period of time tends to become plugged. Efforts to lessen or avoid such plugging, which were tried unsuccessfully, included: filtering the air used in the distribution system; shaving one or more portions of bolts that are inserted through air distribution holes and varying the air distribution rate to different sections of the fluidized bed; and supplementing the fluidizing medium through distribution pipes so as to permit a lessening of the overall flow rate through the distribution plate holes. While all of these methods to some degree lessened the frequency of plugging, they failed to eliminate it for more than about three months at a time.
The spent limestone particles to be cooled have an average overall particle diameter in equivalent spherical dimensions in the range of about 500 to about 1,500 microns. The specific gravity of the particles is in the range of about 2 to about 4, and preferably in the range of about 2 to about 3. The pressure drop across the fluidized bed is in the range of about 30 to about 60 inches of a water column. The air grid pressure drop is in the range of from about 12 to about 40 inches of a column of water. (The maximum differential pressure for the system across the air distribution system from within the distribution boxes to the fluidized bed is about 40 inches of a column of water and the minimum is about 12 inches of a column of water.) The maximum pressure differential of 40 inches is determined by commercial blowers or systems for pressuring vapors that are commonly used in a petroleum refinery. However, larger pressure differentials can be used but do not lead to any significant improvement in performance and might even be deleterious if the pressure drop leads to channeling or loss of fluidized bed material through the air removal system. The minimum differential pressure of about 12 inches is determined by the minimum amount of pressure necessary to maintain equal distribution of the cooling air. The pressure drop across the bed about 30 to 40 inches, is the minimum to maintain a fluidized bed.